Mystery problem Speed 6

[engelborghs]

Hello,

Car : 2005 MK2 4.0L Tuscan, 44.000 Km

Problem: persistently running irregular, slightly improving when properly(>1h running) warm, when cold running on five cylinders and always slow throttle response

So the dealer did a compression test of the six cylinders ......... ALL compression figures where above 11,5 ore around that but cylinder ONE (Not SIX) showed a figures of more then 16 !!!!!
Cylinder SIX exhaust is around 220 degrees whereas the others are around 330 degrees which is normal.

Is there somebody who has an explanation and can it be cured. Can this cause the symptoms?

We found also oil around the spark plugs!!!


PS. Endoscopic inspection of the engine "interior" is healthy.


Koen

[WorAl]

Hmmm sounds an interesting one.....I have no mechanical knowledge, so can't help with the problem, but please keep us posted on anything you find.....could be interesting.

[Hexhamhc]

Could be worth doing a cylinder leak-down test rather than a compression test. Also when did you last have the valve clearances checked and adjusted? It sounds as if there is a potential problem on one cylinder and the above should help to draw a conclusion.
Hope this helps and best regards, Tony Abrams

[Jim Green]

As above, a leak down test will tell you where the problem is.

[engelborghs]

Hexhamhc said:

Could be worth doing a cylinder leak-down test rather than a compression test. Also when did you last have the valve clearances checked and adjusted? It sounds as if there is a potential problem on one cylinder and the above should help to draw a conclusion.
Hope this helps and best regards, Tony Abrams

Hello Tony,

The car is maintained by the Belgian dealer so its done when necessary, I think he mentioned doing it again just to be sure.
"potential problem" >>> potential major problem?

Is it possible that there is a dimension difference between the cylinders in a way that the same displacement can cause higher or lower compressions? I was told that some early Cerbera's had that same issue?


Many Thanks

[nemasis]

sounds like an injector to me

[kevin63]

Have the throttle bodies been balanced?

[engelborghs]

to all,

leak test is OK,

engine out is dangerously close

Koen

[Jim Green]

Sorry to hear that, I guess it's something we'll all face sooner or later.

Amazing how one good drive on a nice sunny day can justify all the work though.

[so called]

Could the oily spark plug be due to valve wear ?
That was my issue, but I also had bad (low) compression figures.

44,00km might be considered "rebuild time" on an earlier Tuscan but opinion is that later cars like your 2005 and later rebuilds should last quite a bit longer.

Good luck.
Tony.